Quarterback Tom Brady’s string of absences will continue into the third phase of the Patriots’ offseason workout program.

Brady won’t attend the voluntary practice Monday at Gillette Stadium, according to a source. It’s the first of 10 organized team activities (OTAs) over the next month.

Brady already skipped the first five weeks of the nine-week offseason workout program at Gillette, but the quarterback himself has noted in the past that the OTAs beginning Monday are the start of the most important stretch during the offseason program. During OTAs and the mandatory minicamp (June 5-7), the offense can practice against the defense without pads or contact.

Brady and tight end Rob Gronkowski both plan to report to Gillette in time for minicamp, according to a source. Gronk has also chosen to stay away from the voluntary portion of the program to this point.

The reason for Brady’s absence hasn’t been made explicitly clear, but there have...